The present invention relates to a fuel-filler inlet for motor vehicles which comprises a closure neck, an insert associated with the closure neck, a filling chamber downstream of the insert, and a filling tube downstream of the filling chambers which leads to a fuel tank.
Nowadays, fuel-filler inlets have to meet particularly high requirements: they are intended to provide good guidance of the fuel nozzle, in order that, during the fuel-dispensing operation, the fuel flow passes smoothly into the filling tube; this means that the latter may be of slender design and does not require a large amount of space. They are intended to ensure that the supply pump in the fuel pump is switched off when the tank is full, for which purpose the opening tube of the fuel nozzle has a so-called expansion port. Poor guidance of the fuel nozzle in the inlet may result in the supply pump being switched off prematurely, which may also be annoying. And, with the presence of ventilation of the fuel vapors, they are not intended to obstruct the same. Of course, they are also intended to be easy to produce and install.
An insert is therefore usually provided in the filler inlet in practice, the inner diameter of the said insert being only slightly larger than the opening tube of the fuel nozzle. However, this simple guidance is not sufficient for positioning the fuel nozzle precisely, and the insert is subjected to pronounced loading on account of the weight of the fuel nozzle. It often consists merely of plastic and ruptures easily.
Such an insert is known, for example, from DE 195 33 306 C1. If the expansion port of the opening tube is provided laterally on the latter and is covered by the insert, switching off the supply pump is not ensured. Fuel may be spilt. With the presence of ventilation, this may even result in liquid fuel passing into the extraction system, which damages the activated-carbon filter.
Furthermore, DE 37 34 782 A1 discloses a filler inlet which has ventilation and a spring-loaded flap valve which does not precisely guide the direction of the fuel nozzle, although it is arranged at a lower level in the filler inlet. This low-level arrangement results in the risk of a lateral expansion port not being reached by the pressure surge which is designed to switch off the pump. Finally, with the fuel nozzle inserted, there is insufficient flow cross section, if any at all, through which air and fuel vapors could escape. Although through-passages are provided in the insert, they are used merely for the flow of air to the closure cap.
It is an object of the invention to configure a filler inlet such that it fulfills all the requirements specified above, namely, good guidance of the fuel nozzle, reliable response of the expansion port and, if appropriate, ventilation during the fuel-dispensing operation.
The foregoing object is achieved according to the invention by providing a collar between the filling chamber and filling tube, the inner-border diameter of which is somewhat larger than that of the opening tube of a fuel nozzle, and forms through-passage openings which, even with the fuel nozzle inserted, produce a flow connection between the filling tube and filling chamber.
The collar is thus provided in addition to the insert, and some distance therefrom, it not being necessary for the insert to project far into the filling chamber. This means that the opening tube of the fuel nozzle is provided with a sufficient guidance length and is guided precisely such that the stream of fuel can flow straight into the filling tube. By way of through-passage openings, pressure surges act reliably on the expansion port of the fuel nozzle and fuel vapors can pass to the ventilation means virtually without obstruction. In addition, and by virtue of its volume, the filling chamber acts as a stabilizing chamber into which, despite the full pressure equalization, it is not possible for any fuel to splash.
The collar is preferably conical. This means that the opening tube of the fuel nozzle is guided into the correct position without the pushing-in action being obstructed. Inexpensive and simple production is achieved if the collar, furthermore, is formed integrally with the wall of the filling chamber. The through-passage openings on the collar may be through-passage holes distributed over the circumference; however, they may also be formed by clearances on the inner border diameter of the collar.
In an embodiment of the invention, the insert has an inwardly directed conical wall, of which the end diameter is somewhat larger than the opening tube of a fuel nozzle, and a flap valve is provided at said inner end. Since the insert need not be positioned so far inward, the filling chamber may give generous dimensions; thus, by way of its volume, it also constitutes a stabilizing chamber and there is sufficient space for the flap valve. The filling chamber may thus also be connected directly to the ventilation means if one is provided.